1. Field of the Invention
The present invention relates to an apparatus for feeding screws or the like, for example, metal rivets or tacks, having head parts and cylindrical shank parts (screwed parts) in such a way as to place the screws in a container, arrange them in lines, and discharge them one after another.
2. Description of the Related Art
A representative example of conventional apparatuses for feeding screws or the like was proposed in [Patent document 1] which was filed by the applicant of the present invention and entitled ‘Screw feeder’. The conventional screw feeder includes a storage container which stores a large number of screws S therein, and a guide rail which is provided in the storage container and extends to the outside of the storage container. The guide rail has an insert rail groove into which the screws S are inserted, and guides the screws S to discharge them in order. Furthermore, the screw feeder further includes a feeding unit which feeds screws S from the storage container onto the rail. The screws S fed onto the rail are moved along the rail and are stopped and arranged in line on a discharge side end of the rail by a stopper.
The feeding unit which feeds the screws S onto the rail includes a board which moves upwards and downwards to lift screws S and put them onto the rail. However, in the conventional technique, because there is a limit to the capacity of the board, many of the screws S which have been in the storage container are not loaded on the board. In other words, even if the size of the storage container is increased, the number of screws which can be loaded on the board is restricted.
Furthermore, because a relatively large number of screws are dropped from the board onto the rail at one time, the screws overlap with each other so that they cannot be satisfactorily arranged in line, with the result that several screws S are discharged at once. That is, the reliability of the operation is low.
In an effort to overcome the above-mentioned problems experienced with the conventional screw feeder, a parts feeding apparatus was proposed in [Patent document 2]. In this technique, a movable plate reciprocates on the outer surface of a storage container which contains metal parts. A magnet is mounted to the movable plate. A scraper is provided at a predetermined position in the storage container. Thus, a small amount of metal parts are scooped up from the storage container using the magnetic force of the magnet. The scraper scrapes the metal parts off the magnet. Thereafter, the metal parts are discharged to the outside one by one. However, although this apparatus can feed parts one by one, because the movable plate reciprocates, the apparatus is complicated and abrasion of the elements is increased. Furthermore, since the metal parts are separated from the magnet in such a manner that the scraper scrapes the metal parts off the magnet, the metal parts may be easily damaged. Thus, various kinds of transporting members or receiving members are required.    [Patent document 1] Japanese Patent Laid-open Publication No. Heisei. 9-58847    [Patent document 2] Japanese Patent Laid-open Publication No. 2001-287827